More Science and Visuals from Greenland

July 1, 2013

Extreme contrasts between warm, moist air, and cold dry air, make for rapid and dramatic change in the environment of coastal Greenland, as evidenced in this mysterious fog effect over Sisimiut.

Jason Box and Sara Penrhyn Jones at work in our Sisimiut base. There’s a great synergy here among the three of us passing images, dialogue and expertise back and forth. It’s like a high end graphic shop transplanted from Brooklyn or San Francisco to a tiny cottage on the rocky coast of Greenland.

Surface reflectivity of sunlight is called “albedo”. Albedo is a Latin-based word referring to whiteness. The higher the albedo, the more sunlight can be reflected. As albedo decreases, more sunlight can be absorbed.

The absorption of sunlight is the largest single source of melt energy on the Greenland ice sheet.

During melting, the rounding of ice crystals by heating causes the albedo to drop.

A freshly fallen snow crystal has numerous facets to reflect sunlight (left). Warming causes the grains to round at the edges and clump together (right). Scanning electron microscope photos courtesy the Electron and Confocal Microscopy Laboratory, USDA Agricultural Research Service.

In some areas of the ice sheet, by the time winter snow cover melt away, bare glacier ice is exposed. Where impurities congregate, the surface albedo drops below 30%.

12 August 2005, 8 PM local time, I took this photo from a helicopter flying over the ice sheet surface at ~1500 feet altitude. This is how much darker the Greenland ablation area is than a fresh snow surface that blankets it in wintertime. Along much of the southwestern ice sheet at the lowest 1000 m in elevation, impurities concentrate near the surface and produce this dark surface. Not all of the ice sheet is this dark, only the lower ~1/3 of the elevation profile of the ice sheet is. However, as melting increases on the ice sheet, so does the area exposed that is this dark.

As part of Dark Snow Project’s 2013 expedition, Dr. Marek Stibal gathers samples from an area of concentration near the darkest point on the Western Greenland ice sheet.

An increase in atmospheric heating of Greenland ice is a driver of Greenland ice albedo decline in summer, in part due to the expansion of bare ice areas, in part due to the heating effect on rounding ice crystals, and in part if the concentration of impurities increases.

In the period of high quality observations beginning early 2000, June 2013 albedo for the ice sheet is ranked 3rd lowest.

Greenland albedo started out very low in 2013 due to a snow drought exposing darker bare ice around the ice sheet periphery.

The albedo feedback with climate is responsible for doubling the temperature changes when climate warms or cools. This amplifier helps Earth’s climate system swing into and out of ice ages. The feedback is complex, including the effects of heating and light absorbing impurities, in a process that compounds through time.

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